1. Field of the Invention
The present invention relates to a cross coil type indicating gauge, particularly to a cross coil type indicating gauge mounted on automobiles and suitable for speed meters, tachometers, boost gauges, oil pressure gauges, etc.
2. Description of the Prior Art
An indicating gauge for automobiles has been widely used in the past, in which a current that varies in response to the amount of a measurement is caused to flow through a pair of coils that generate magnetic fields at right angles to each other, said pair of coils cause a magnet rotor to rotate in the direction of the combined magnetic field which is formed of the magnetic fields generated by each of said pair of coils, and the measurement amount is displayed by means of a pointer rotating together with the magnet rotor.
This kind of conventional indicating gauge is formed of a cross coil in which two coils are wound at right angles to each other on the outside of a coil bobbin. In the center of the inside of this coil bobbin is disposed a magnet rotor held rotatably inside said cross coil and in which the south pole and the north pole are formed at diametrically symmetrical positions. A rotation shaft passing through said cross coil is secured to the center of said magnet rotor. The movement of a gauge is formed by the above-described arrangement. The above movement is mounted on the rear side of a gauge board, and the pointer is mounted to the tip of said rotation shaft passing through said gauge board, which forms an indicating gauge.
In the conventional indicating gauge described above, a current that varies in response to the amount of a measurement is caused to flow through each of the above coils. This causes the magnet rotor to rotate in the direction of the combined magnetic field which is formed of the combined magnetic fields generated by each of the coils, which causes the above pointer to rotate via said rotation shaft to display the amount of a measurement.
In recent years, one such that a plurality of said indicating gauges are arranged on a single gauge board for improved space efficiency has appeared. For example, when two movements are used, those movements are arranged in parallel, and a pointer mounted on each rotation shaft is arranged in the front of a single gauge board. However, in such an arrangement, the problem that each rotation shaft is located apart from the other, making the distance between the pointers great, has been posed.
For this reason, there has been one from the past such that a rotation gear is secured to said rotation shaft, a counter shaft to which a counter gear that engages this rotation gear is secured, is rotatably disposed to a coil bobbin, and the rotation center of said pointer is off-centered from the rotation shaft. This enables the pointers to be closely disposed even when two movements are disposed in parallel, with the result that the distance between the pointers becomes small, and space can efficiency be utilized. Furthermore, if three movements are used and the counter shafts of the movements are disposed closely, the three pointers will be formed in such a layout that each of them radially extends from the center of the gauge board, further improving space efficiency.
In the above indicating gauge whose pointer is off-centered, when returning said pointer to the 0 position of the gauge board, a hair spring is mounted on said counter shaft, and said pointer is made to return by the energization force of said hair spring under the condition that said coil is not supplied with electric current, and the magnet rotor is not applied with a torque. As a means of stopping this pointer at the 0 position, conventionally, a stopper pin is projected in the 0 position of a gauge board, and said pointer is stopped by means of this stopper pin.
In the conventional indicating gauge described above, generally, teeth have been formed only to portions needed to rotate said pointer to a predetermined angle in a counter gear, and said counter gear is secured so that the end parts of the tooth formed part correspond to the 0 position indicated by said pointer. However, since said counter shaft is energized by a hair spring, said counter gear may rotate by this energization force after said counter gear is mounted. So, there is a possibility that the engagement of the tooth-formed part of said counter gear and the rotation gear may slip out of place, and the problem that the work of securing the counter gear to said counter shaft is difficult, is posed. Moreover, a stopper pin must be formed in said gauge board so that said counter gear will not rotate to the position at which portions other than said tooth-formed parts correspond to the rotation gear. This results in an increase in the number of parts, leading to increased assembly processess.
In light of the above-described deficiencies, the present invention has been devised. An object of the invention is to provide a cross coil type indicating gauge capable of returning a pointer reliably to the 0 position without forming a stopper pin in an gauge board, and for which assembly of counter gears is easy.
Another object of the invention is to provide a cross coil type indicating gauge of which the number of parts can be reduced, and that can be manufactured easily and at a low cost.